The present invention relates to a method and an apparatus for network connection, which interconnect various networks, e.g., a Local Area Network (LAN) with a wide area network or the like. More particularly, the invention relates to a -method and an apparatus for network connection, which perform communication channel allocation for the wide area network in order to ensure communication quality.
Communications between private networks located in remote areas must be carried out through a wide area communication network. Also, data communications carried out by connecting the LAN with the wide area communication network must employ a network connecting device called a router. In this case, depending on differences in communication systems among wide area networks to be utilized, a method for providing a communication channel to the router may vary in a following manner.
A circuit switching system is available as one of the communication systems among the wide area communication networks. In this system, communication lines are linked beforehand between a user and a switching system and between switching systems. But none of the lines is closed, and no communication channels are provided between users in a normal state. To provide a communication channel for connecting specific two points, communication lines are connected to each other in the switching system by signaling process corresponding to a connection destination that a user specifies by calling before the start of communications. Such a method of transferring communication data, which is accompanied by call control processing, is called a connection-oriented transmission.
In the case of a device called a dial-up router, a connection destination is specified based on protocol control information of packet data carried on a LAN, and the packet data on the LAN is transmitted to the communication channel provided by the foregoing system. Accordingly, inter-LAN communications can be carried out by changing connection destinations when necessary. Similarly, in the circuit switching system, by using the communication channel provided by the communication line which connects the predetermined two points beforehand, the need to perform signaling process can be eliminated at each starting of communications. The communication line provided in such a manner is called a leased line. In the case of a device called a remote router, inter-LAN communications can be carried out by transmitting packet data on the LAN to the communication channel on the leased line.
There is another different communication system called a packet switching system. Also, for this system, communication lines are linked beforehand between a user and a switching system and between switching systems. In the packet switching system, however, communication lines are not so configured as to connect predetermined two points before the start of communications by signaling or a leased line like that in the circuit switching system. Instead, each switching system interprets protocol control information of the packet data on the LAN and, then, by selecting a switching system of a transfer destination and repeating transfer, transmits the packet data to a LAN of communication destination. Thus, one communication channel is always provided to the user and, by using this channel, the user can communicate with all the LANs that need to be connected. Such a method of transferring communication data, which is not accompanied by any signaling process, is called a connectionless transmission.
There is yet another system called an Asynchronous Transfer Mode (ATM) communication system. In this system, as in the case of the circuit switching system, a communication channel to connect predetermined two points is allocated corresponding to a connection destination that a user specifies by calling before the start of communications. But a communication line between switching systems is not directly connected, and only the correspondence thereof is held. A logical number for identifying the correspondence is provided to the user as a number for identifying the communication channel. The user adds this logical number to packet data, and then transmits the data. Each switching system selects a communication line to be used for transfer based on the logical number added to the packet data. Accordingly, a plurality of communication channels can be provided separately by one communication line. Also, by means of setting made beforehand as in the case of the circuit switching system, a predetermined communication channel can be used as a permanently set leased line.
In any of the above systems, it is necessary to establish correspondence between the protocol control information of the packet data on the LAN and the communication channel provided by the wide area communication network. As a method for this purpose, a Multi-Protocol over ATM (MPOA) is available, which makes a detailed description especially of the ATM communication system. In accordance with this method, a device having an address translation function and a packet switching function is provided on the communication network of the ATM system, and a communication channel for communicating with the device is permanently set. The user can transmit the data packet on the LAN to the permanently set communication channel, and can also transmit the packet data to a newly set communication channel by using the address translation function to decide a connection destination.
For data communications on the wide area communication network, if the packet switching system is used, which multiplexes all packet data on one communication channel, it is difficult to maintain, for a long time, communication quality such as assurance of a constant bandwidth keeping of constant transmission delay time or the like. On the other hand, if the circuit switching system is used, which allocates individual communication channels for respective data communications, data packets from the LAN can stay in the network connecting device during signaling process for allocating the communication channels. Therefore if the communication traffic is heavy, the data packet may be discarded, and normal communications may not be established. If the leased line is used, since a communication line connected to a specified opposite point is continuously held even when there is no data packet to be transmitted, efficiency may be reduced.
Also, in the case of logically setting communication channels by the packet switching system or the ATM communication system, similar cases may occur. This is because switching system resources are held by setting of each switching system or by. reservation for use of a buffer or the like.
It is therefore an object of the present invention to prevent data packets from staying in the network connecting device during allocation of individual communication channels for respective communications. This is achieved by selecting a connectionless transmission network such as the packet switching system or the leased line and a connection-oriented transmission network such as the circuit switching system. In this case, according to the invention, a plurality of networks operated by different subjects are used in free combination while the connectionless transmission network and the connection-oriented transmission network are kept independent of each other. Also, another object of the invention is that under an artificially specified condition one to be used for communications is selected from the plurality of networks and used.
Regarding allocation of individual communication channels for respective data communications, allocation is carried out in the starting order of communications. In this case, if a transfer capability of the network reaches saturation, no new communication channels can be allocated for subsequent new data communications. Consequently, the network may be occupied by the existing users in the circuit switching system, and new users cannot make instantaneous use of the network. Also, in the packet switching system, communication quality provided by the entire network may deteriorate.
It is therefore an object of the present invention to allocate communication channels for subsequent data communications according to the necessity thereof. This allocation is achieved by preventing communication lines from being occupied by the previous users while preventing deterioration of communication quality provided by the entire network or a reduction in line use efficiency. The present invention is also aims to allow quality deterioration can be limited to only partial communication data. This is achieved by switching the communication channels that respective communication data use, in connection with a state of congestion of the communication lines.
Yet another object of the invention is, among data communications set priorities, to allocate an individual communication channel to data communications having a highest priority and enable the data communication to be started, without holding unused a part of a communication line capacity beforehand and irrespective of the starting order of data communications. In this case, even data communications having a lowest priority can be continued.
In accordance with, the first solving means of the present invention, a network connecting method in a network connecting device, the network connecting device including:
first communicating means for performing communications with a first communication network such as a local area network;
connectionless (CL) communicating means for performing a CL transmission with a second communication network; and
connection-oriented (CO) communicating means for performing a CO transmission with a third communication channel,
the network connecting method comprising the steps of:
storing in first storing means at least a part of protocol control information and communication channel identifying information in a corresponding relationship, the protocol control information being of data on the first communication network, and the communication channel identifying information being for identifying a communication channel with a second, alternatively third wide area communication network; and
performing channel control for changing a entry having communication channel identifying information which indicates the CO communicating means to a entry having communication channel identifying information which indicates the CL communicating means, by referring to the communication channel identifying information held in the first storing means.
In accordance with the second solving means of the invention, a network connecting method in a network connecting device, the network connecting device including:
first communicating means for performing communications with a first communication network such as a local area network;
connectionless (CL) communicating means for performing a CL transmission with a second communication network; and
connection-oriented (CO) communicating means for performing a CO transmission with a third communication network,
the network connecting method comprising the steps of:
storing in first storing means at least a part of protocol control information and communication channel identifying information in a corresponding relationship, the protocol control information being of data on the first communication network, and the communication channel identifying information being for identifying a communication channel with a second, alternatively third wide area communication network; and
performing channel control for recovering a entry having communication channel identifying information which indicates the CL communicating means as a entry having communication channel identifying information which indicates the CO communication means, by referring to the communication channel identifying information held in the first storing means.
In accordance with the third solving means of the invention, a network connecting device comprising:
first communicating means for performing communications with a first communication network such as a local area network;
connectionless (CL) communicating means for performing CL transmission with a second communication network;
connection-oriented (CO) communicating means for performing a CO transmission with a third communication network;
first storing means for storing at least a part of protocol control information and communication channel identifying information in a corresponding relationship, the protocol control information being of data on the first communication network, and the communication channel identifying information being for identifying a communication channel with a second, alternatively third wide area communication network; and
channel control means for changing a entry, which has communication channel identifying information indicating the CO communicating means to a entry, which has communication channel identifying information indicating the CL communicating means, by referring to the communication channel identifying information held in the first storing means.
In accordance with the fourth solving means of the invention, a network connecting device comprising:
first communicating means for performing communications with a first communication network such as a local area network;
connectionless (CL) communicating means for performing a CL transmission with a second communication network;
connection-oriented (CO) communicating means for performing a CO transmission with a third communication network;
first storing means for holding at least a part of protocol control information and communication channel identifying information in a corresponding relationship, the protocol control information being of data on the first communication network, and the communication channel identifying information being for identifying a communication channel with a second, alternatively third wide area network; and
channel control means for recovering a entry, which has communication channel identifying information indicating the CL communicating means, as a entry which has communication channel identifying information indicating the CO communicating means, by referring to the communication channel identifying information held in the first storing means.
In accordance with the fifth solving means of the invention, a network connecting device comprising:
first communicating means for performing communications with a first communication network such as a local area network;
connectionless (CL) communicating means for performing a CL transmission with a second communication network;
connection-oriented (CO) communicating means for performing a CO transmission with a third communication network;
first storing means for holding at least a part of protocol control information and communication channel identifying information in a corresponding relationship, the protocol control information being of data on the first communication network, and the communication channel identifying information being used by the CL and CO communicating means;
second storing means for holding the at least a part of protocol control information and sequence information in a corresponding relationship, the protocol control information being of data on the first communication network, and the sequence information for sequencing;
channel setting control means for adding a new first entry containing at least a part of the protocol control information of data on the first communication network to the first storing means, and updating communication channel identifying information of the first entry to one for using the CL communicating means; and
kicking-out means for deciding, among entries using the CO communicating means, a entry to be changed to one for using the CL communicating means by referring to at least a part of protocol control information of a data packet held in the first storing means and the sequence information held in the second storing means, and then updating the communication channel identifying information held in the first storing means to indicate the CL communicating means for the decided entry.
In order to solve the foregoing problems, an Internet switching system of the present invention is a network connecting device designed to connect a LAN to a wide area communication network. This network connecting device comprises: communicating means for performing a connectionless transmission with the wide area communication network; communicating means for performing a connection-oriented transmission with the wide area communication network; first storing means for holding, in a corresponding relationship, a part or all of protocol control information of a data packet on the LAN, information for identifying communicating means with the wide area communication network, information for identifying a communication channel to be used in the communication means, information for identifying a connection destination of the communication channel, information for indicating communication capabilities such as a communication band or quality provided by the communication channel, a logical true/false value for determining time-out, which indicates a used state of the communication channel, and an integral value for ordering; means for updating the logical true/false value for time-out determination to be false by referring to the protocol control information of the data packet on the LAN and the information held in the first storing means, and then transferring the data packet by using the communicating means with the wide area communication network; second storing means for holding, in a corresponding relationship, a part or all of the protocol control information of the data packet on the LAN, a time zone, an integral value indicating priority, and information indicating a required communication band or quality; means for deciding a communication channel to be used by the transmitting means with the wide area communication network by referring to the protocol control information of the data packet on the LAN and the information held in the second storing means, and then updating the information held in the first storing means; means for selecting from the information held in the first storing means one item having a communication channel used for a connectionless transmission, and one item having a communication channel used for a connection-oriented transmission, both ones having the identical information for identifying a communication channel connection destination, and then switching the information for identifying the communication channels therebetween, thus updating the information thereof; means for updating a false logical true/false value for determining time-out to be true at every constant interval of time by referring to the information held in the first storing means; means for selecting one item having a communication channel for the connectionless transmission, and one item having a logical true/false value set true for time-out determination, from. those which have the same information for identifying a communication channel connection destination from the information held in the first storing means at every constant interval of time, and then switching the information for identifying the communication channel therebetween, thus updating the information thereof; and means for sorting the items in order in accordance with an integral value for ordering by referring to the information held in the first storing means.
Furthermore, a method for controlling the means for deciding the communication channel used for the communicating means includes the steps of: storing in the first storing means, in a corresponding relationship, a part or all of the protocol information of a data packet on the LAN, the information for identifying communicating means for performing a connectionless transmission with the wide area communication network, information for identifying a preset communication channel used by the communicating means, and setting a logical true/false value for determining time-out for the item to be false; if the protocol control information of the data packet on the LAN coincides with the information held in the second storing means, performing call setting control for setting a communication channel to be used by communicating means by using the communicating means for performing a connection-oriented transmission with the wide area communication network; if the call setting control in the previous step succeeds, updating, among the items stored in the first storing means in the previous step, the information for identifying the communication channel, the information for identifying the communication channel connection destination, the logical true/false value for time-out determination, and the integral value for ordering; and if the call setting control in the previous step fails, using means that selects, from the information held in the first storing means, one item having the communication channel for the connectionless transmission and one item having the communication channel for the connection-oriented transmission, and then switches and updates the information for identifying the communication channels therebetween. The communication channels used in data packet communication on the LAN can be switched successively when necessary, using the network connecting device.